Medical research directed to the removal or abatement of coronary stenoses and other vascular obstructions has generated a variety of therapies and surgical and nonsurgical procedures, as well as sophisticated equipment both to perform and to monitor these procedures. A procedure of increasing popularity is percutaneous transluminal angioplasty since it does not involve thoracotomy. Consequently, angioplasty poses a lesser risk of postoperative complications such as postperiocardotomy syndrome, hepatitis, and stroke, plus a lesser risk of mortality, while allowing a faster recovery of the patient. In addition, recent surveys have shown that the effectiveness of angioplasty compares well with that of surgical techniques, in terms of the abatement of coronary obstructions as well as the incidence of the reoccurrence of such obstructions.
Angioplasty techniques have their limitations, however, and these are particularly pronounced in situations where the coronary restriction is severe. In conditions where the plaque which causes the obstruction spans the cross section of the vessel entirely, it may not be possible to penetrate and span the obstructed region with the angioplasty balloon. Also, since angioplasty merely compresses the plaque against the vessel wall rather than removing it, the procedure may be of limited effect, or susceptible to an early reoccurrence of the obstruction. To address these concerns, catheters and catheter systems have been developed which loosen and remove the plaque from the vessel rather than merely compressing it. Loosening is achieved by a variety of ablation techniques, such as cutting, abrasion, emulsification and the use of ultrasound or lasers, while removal is achieved through lumens in the catheter shafts. Even with techniques such as these, however, it is not possible to remove all plaque from the obstructed vessel, and plaque which has been loosened but not removed creates a risk of acute problems subsequent to the procedure, recurrence of the blockage condition, or both. A further problem encountered in both angioplasty and plaque loosening and removal techniques is that these procedures are performed while the heart is still beating. The movement caused by the beating heart makes it difficult to determine the precise location of the plaque and to effect its complete removal.